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    Ingredient guide · Ingredient reference

    Soy protein isolate: the nine essential amino acids in a reference serving

    Soy isolate contains all nine essential amino acids in this USDA record. The quantities belong to a specified ingredient, not every finished soy-protein product.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    Identify the ingredient and denominator

    USDA SR Legacy lists soy protein isolate at 88.32 g protein per 100 g ingredient. Its amino-acid record includes all nine essential amino acids named by NIH ODS. A hypothetical 30 g portion supplies 26.496 g protein, rather than 30 g of pure protein. [1][2]

    Presence and protein quality are separate

    The table gives each essential amino acid for that 30 g portion. It does not measure digestion in an individual or independently assay a retail shake. A finished product with flavors, carbohydrate or other proteins needs its own declaration; dilution changes the amount supplied by an equal scoop weight. [2]

    A hypothetical portion adjustment

    A 15 g portion of this reference ingredient provides half the table’s quantities, including 1.017 g leucine and 0.799 g lysine. Use the actual ingredient weight and product composition before comparing with a dietary target. These values do not establish a required supplement dose. [1]

    Hypothetical example — calculate specified food portions from historical reference data
    Essential amino acidEstimate in 30 g soy isolate
    Tryptophan0.335 g
    Threonine0.941 g
    Isoleucine1.276 g
    Leucine2.035 g
    Lysine1.598 g
    Methionine0.339 g
    Phenylalanine1.378 g
    Valine1.229 g
    Histidine0.691 g
    Soy protein isolate: the nine essential amino acids in a reference serving — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. USDA FoodData Central — SR Legacy April 2018 composition and portion tables
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.
    2. Dietary Supplements for Exercise and Athletic Performance - Health Professional Fact Sheet
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.